164 PROCEEDINGS OF THE AMERICAN ACADEMY. 



observed a maximum in the molecular conductivity of a 0.01 normal 

 KC1 solution. In all of these experiments the conductivity cell was 

 made of glass and was necessarily very small ; therefore, owing to the 

 solubility of glass at these temperatures and to the danger of polariza- 

 tion of the small electrodes used, the results have little significance. 



Believing that accurate conductivity measurements through a wide 

 range of temperature extending up to or nearly to the critical point 

 would yield results of considerable theoretical interest, we have under- 

 taken an investigation in this direction. 



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The first and most difficult part of this research consisted in the con- 

 struction of a conductivity cell composed internally of material unacted 

 upon by aqueous solutions and capable of withstanding without leakage 

 the high vapor-pressure of such solutions up to the critical temperature. 

 After working continuously for three years upon this problem, we have 

 succeeded in overcoming the mechanical difficulties and in constructing a 

 platinum-lined bomb with insulated electrodes which remains perfectly 

 tight at any rate up to 306°, which occasions only an unimportant con- 

 tamination even in salt solutions as dilute as -^oW m °l a, % which yields 

 conductivity measurements accurate to 0.25 per cent or less, and which 

 at the same time makes possible specific-volume determinations, which 

 are essential to the interpretation of the results. Now that a knowledge 

 of the necessary mechanical devices has been acquired, the making of 

 such a bomb is an easy task for a skilled instrument maker. We shall, 

 therefore, in this article first describe in full detail, with the help of 

 working drawings, the apparatus used, and especially the construction 

 of the bomb, in order to make it readily available for investigators who 

 desire to pursue researches of the same kind or those requiring similar 

 apparatus (such, for example, as a calorimetric bomb). 



We have thus far been able to investigate only two dissolved sub- 

 stances, — potassium and sodium chloride, — but have made conductivity 

 and specific volume measurements with their solutions at various tempera- 

 tures ranging from 26° to 306° and at various concentrations between 



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0.1 and 0.0005 molar. The work will be extended during the coming 

 year to other substances, and if possible to the critical temperature ; but 

 as it will be carried on in part by other workers and under the auspices 

 of the Carnegie Institution, it has seemed appropriate to publish the 

 results already obtained, especially as these seem to justify several 

 interesting conclusions of a general character. 



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In concluding these introductory statements it gives us much pleasure 

 to acknowledge our great indebtedness to the American Academy of 



